Most laparoscopic and open surgical procedures require some "blunt" anatomical dissection to, for example, separate the tissue and hold the tissue out of the way of the operating site. In laparoscopic surgery, dissection is done most commonly with electrical cautery or, in some procedures, using thin mechanical dissectors, sometimes combined with cauterization. Both of these approaches present the possibility of perforation of the dissected organ.
A number of different mechanical dissectors have been used in surgical procedures. Patents of interest or possible interest in the broad field of medical manipulators and in other medical fields include the following: U.S. Pat. Nos. 5,284,128 (Hart); 5,195,968 (Lundquist et al.); 4,998,527 (Meyer); 4,807,626 (McGirr); 4,271,845 (Chikashige et al.); and 3,730,185 (Cooke et al.).
The Hart patent discloses a surgical manipulator having a long outer tube with a distal end and a proximal end. The proximal end is connected to a handle. The distal end is constructed so that one sidewall of the outer tube is relatively weak compared to the opposite sidewall. An inner tube, smaller in diameter than the outer tube, is positioned longitudinally within the outer tube and the distal ends of the inner and outer tubes are connected together while the proximal end of the inner tube is connected to a finger tab that is slidably located on the handle. When the finger tab is slid forward or backward in relation to the handle, the tab creates a compression or tension in the inner tube. The inner tube translates that force to the outer tube at the distal connection, and in response to that force, the outer tube curls in one direction, either toward or away from the weaker wall, depending on whether the force is compression or tension. Thus, the end of the outer tube (as well as the inner tube encased within) can be made to curl in either of two directions. The patent discloses that the inner element could be in the form of a wire rather than a tube. By using a tube as the inner element, however, the device allows the insertion of other laparoscopic devices through the inner opening as well as allowing suction of fluid from the body cavity back through the opening.
The Lundquist et al patent discloses a steering mechanism for use with a catheter. The mechanism includes a hollow tube with a proximal end connected to a handle and a flexible distal end having a flat lead spring mounted therewithin. The lead spring serves to provide memory for the distal end so that the distal end reverts to its straightened position when not under tension. Longitudinally positioned within the hollow tube is a steering wire that is connected to the lead spring at its distal end and to one of several tension producing mechanisms at its proximal end in the handle. When tension is placed on the steering wire the distal end of the tube curls in the direction of the side of the spring to which the wire is connected. In another embodiment, two steering wires can be used so that the tube can be forced to curl in either of two opposite directions. Because the device is designed only to steer a catheter, it is not adapted to carry other instruments or to allow fluid flow within the tube.
The Chikashige et al. patent discloses a device for guiding a medical instrument by bending a shaft that holds the end of the instrument. The outer shaft is a cylindrical coil or spring. The distal end of the coil is coarsely wound and has one sidewall weaker than its opposing sidewall. The different sidewall strengths can be accomplished through a number of illustrated methods. A wire is longitudinally positioned through the center of the spring and connected to the distal end of the spring. Tension placed on the wire causes the distal end of the spring to curl in a direction away from the weaker sidewall, thus guiding the medical instrument that is attached to the distal end of the spring. The patent also provides for a control wire to be longitudinally positioned within the spring for operating instruments such as forceps that may be attached to the distal end of the spring.
The McGirr patent discloses a stone extractor for use within body cavities which includes a tube with a distal end connected to a self-closing basket and a control wire longitudinally positioned within the tube for opening the basket. The patent provides that fluids can flow through the interior of the tube. In one embodiment, the tube is made from a flexible material that has elastic memory and is formed with a predetermined curvature. A rigid sleeve is slid over the tube to keep it straight as the tube is inserted through an endoscope and the sleeve is retraced to allow the tube to resume its pre-formed curl once inside the cavity. In this manner the basket is guided to its desired location.
The Meyer patent discloses an endoscope tissue removing device performing multiple functions necessary for viewing and resecting tissue. The distal end of an inner tube is rotated in relation to an outer tube to aid in resecting the tissue.
The Cooke et al. patent discloses a method of removing arteriosclerotic material from an artery. The distal end of a rod is formed into a loop and is oscillated to cause a separation of the material from the artery.